scholarly journals Transcriptional activity and epigenetic regulation of transposable elements in the symbiotic fungus Rhizophagus irregularis

2021 ◽  
Author(s):  
Alexandra Dallaire ◽  
Bethan F. Manley ◽  
Maya Wilkens ◽  
Iliana Bista ◽  
Clement Quan ◽  
...  
Keyword(s):  
Dna Methylation ◽  
Transposable Elements ◽  
Small Rna ◽  
Clonal Evolution ◽  
Arbuscular Mycorrhizal ◽  
Am Fungi ◽  
Gene Families ◽  
Land Plant ◽  
Rhizophagus Irregularis ◽  
Genomic Diversity

Arbuscular mycorrhizal (AM) fungi form mutualistic relationships with most land plant species. AM fungi have long been considered as ancient asexuals. Long-term clonal evolution would be remarkable for a eukaryotic lineage and suggests the importance of alternative mechanisms to promote genetic variability facilitating adaptation. Here, we assessed the potential of transposable elements for generating such genomic diversity. The dynamic expression of TEs during Rhizophagus irregularis spore development suggests ongoing TE activity. We find Mutator-like elements located near genes belonging to highly expanded gene families. Whole-genome epigenomic profiling of R. irregularis provides direct evidence of DNA methylation and small RNA production occurring at TE loci. Our results support a model in which TE activity shapes the genome, while DNA methylation and small RNA–mediated silencing keep their overproliferation in check. We propose that a well-controlled TE activity directly contributes to genome evolution in AM fungi.

scholarly journals Transcriptional activity and epigenetic regulation of transposable elements in the symbiotic fungus Rhizophagus irregularis

2021 ◽  
Author(s):  
Alexandra Dallaire ◽  
Bethan F Manley ◽  
Maya Wilkens ◽  
Iliana Bista ◽  
Clement Quan ◽  
...  
Keyword(s):  
Dna Methylation ◽  
Transposable Elements ◽  
Small Rna ◽  
Clonal Evolution ◽  
Arbuscular Mycorrhizal ◽  
Am Fungi ◽  
Gene Families ◽  
Land Plant ◽  
Rhizophagus Irregularis ◽  
Genomic Diversity

Arbuscular mycorrhizal (AM) fungi form mutualistic relationships with most land plant species. AM fungi have long been considered as ancient asexuals. Long-term clonal evolution would be remarkable for a eukaryotic lineage and suggests the importance of alternative mechanisms to promote genetic variability facilitating adaptation. Here, we assessed the potential of transposable elements (TEs) for generating genomic diversity. The dynamic expression of TEs during Rhizophagus irregularis spore development suggests ongoing TE activity. We find Mutator-like elements located near genes belonging to highly expanded gene families. Characterising the epigenomic status of R. irregularis provides evidence of DNA methylation and small RNA production occurring at TE loci. Our results support a potential role for TEs in shaping the genome, and roles for DNA methylation and small RNA-mediated silencing in regulating TEs. A well-controlled balance between TE activity and repression may therefore contribute to genome evolution in AM fungi.

scholarly journals Histone H1 prevents non-CG methylation-mediated small RNA biogenesis in Arabidopsis heterochromatin

2021 ◽  
Author(s):  
Jaemyung Choi ◽  
David Bruce Lyons ◽  
Daniel Zilberman
Keyword(s):  
Dna Methylation ◽  
Transposable Elements ◽  
Small Rna ◽  
Histone H3 ◽  
Histone H1 ◽  
Dna Methyltransferases ◽  
Flowering Plants ◽  
Genomic Sequences ◽  
Rna Molecules ◽  
Rna Biogenesis

Flowering plants utilize small RNA molecules to guide DNA methyltransferases to genomic sequences. This RNA-directed DNA methylation (RdDM) pathway preferentially targets euchromatic transposable elements. However, RdDM is thought to be recruited by methylation of histone H3 at lysine 9 (H3K9me), a hallmark of heterochromatin. How RdDM is targeted to euchromatin despite an affinity for H3K9me is unclear. Here we show that loss of histone H1 enhances heterochromatic RdDM, preferentially at nucleosome linker DNA. Surprisingly, this does not require SHH1, the RdDM component that binds H3K9me. Furthermore, H3K9me is dispensable for RdDM, as is CG DNA methylation. Instead, we find that non-CG methylation is specifically required for small RNA biogenesis, and without H1 small RNA production quantitatively expands to non-CG methylated loci. Our results demonstrate that H1 enforces the separation of euchromatic and heterochromatic DNA methylation pathways by excluding the small RNA-generating branch of RdDM from non-CG methylated heterochromatin.

Novel Insights into Host Receptors and Receptor-mediated Signaling that Regulate Arbuscular Mycorrhizal Symbiosis

2020 ◽  
Author(s):  
Fahad Nasir ◽  
Ali Bahadur ◽  
Xiaolong Lin ◽  
Yingzhi Gao ◽  
Chunjie Tian
Keyword(s):  
Host Plant ◽  
Host Plants ◽  
Agronomic Traits ◽  
Arbuscular Mycorrhizal ◽  
Am Fungi ◽  
Land Plant ◽  
Physical Contact ◽  
Mycorrhizal Symbiosis ◽  
Downstream Signaling ◽  
Am Symbiosis

Abstract More than 80% of land plant species benefit from symbiotic partnerships with arbuscular mycorrhizal (AM) fungi that assist in nutrient acquisition and enhance the ability of host plants to adapt to environmental constraints. Host-generated plasma membrane-residing receptor-like kinases and the α/β-hydrolases, e.g. DWARF14-LIKE (D14L), a putative karrikin receptor, are used to detect the presence of AM fungi prior to physical contact between the host and fungus. Detection induces the activation of symbiosis-related transcriptional programming, enabling the successful establishment of AM symbiosis. In order to prevent hyper-colonization and to maintain a mutually beneficial association, the host plants precisely monitor and control AM symbiosis during the post-symbiotic stage via different molecular strategies. While previous studies have elucidated how host plant receptors and receptor-mediated signaling regulate AM symbiosis, the molecular details underlying these processes remain poorly understood. The recent identification of a rice (Oryza sativa) CHITIN-ELICITOR RECEPTOR-KINASE 1 (OsCERK1) interaction partner MYC FACTOR RECEPTOR 1 (OsMYR1), as well as new insights into D14L-receptor- and SUPER NUMERIC NODULES 1 (SUNN1) receptor-mediated signaling have improved our understanding of how host plant receptors and their corresponding signaling regulate AM symbiosis. The present review summarizes these and other current findings that have increased our limited understanding of receptor-mediated signaling mechanisms involved in the regulation of AM symbiosis. The identified receptors and/or their downstream signaling components could potentially be used to engineer economically-important crops with improved agronomic traits by conferring the ability to control the colonization of AM fungi in a precise manner.

Mycorrhizal fungi

2009 ◽  
Author(s):  
M. Anwar Maun
Keyword(s):  
Mycorrhizal Fungi ◽  
Higher Plants ◽  
Sand Dunes ◽  
Arbuscular Mycorrhizal ◽  
Am Fungi ◽  
Coastal Dunes ◽  
Active Role ◽  
Land Plant ◽  
Vital Functions ◽  
Mycorrhizal Interactions

Mycorrhizal fungi (mycobionts) form a ubiquitous mutualistic symbiotic association with the roots of higher plants (phytobionts) in coastal sand dunes worldwide. These obligate biotrophs perform vital functions in the survival, establishment and growth of plants by playing an active role in nutrient cycling. As such they serve as a crucial link between plants, fungi and soil at the soil–root interface (Rillig and Allen 1999). Mycorrhizas occur in a wide variety of habitats and ecosystems including aquatic habitats, cold or hot deserts, temperate and tropical coastal dunes, tropical rainforests, saline soils, volcanic tephra soils, prairies and coral substrates (Klironomos and Kendrick 1993). Simon et al. (1993) sequenced ribosomal DNA genes from 12 species of arbuscular mycorrhizal (AM) fungi and confirmed that mycorrhizas (fungal roots) fall into three families. He estimated that they originated about 353–462 million years ago and were instrumental in facilitating the colonization of ancient plants on land. Further evidence was provided by Remy et al. (1994) who discovered arbuscules in an early Devonian land plant, Aglaophyton major, and concluded that mycorrhizal fungi were already established on land > 400 million years ago. Thus the nutrient transfer mechanism of AM fungi was already in existence before the origin of roots. Plant roots probably evolved from rhizomes and AM fungi served as an important evolutionary step in the acquisition of water and mineral nutrients (Brundrett 2002). Over evolutionary time the divergence among these fungi has accompanied the radiation of land plants, and about 200 species of AM fungi have been recognized (Klironomos and Kendrick 1993) that exist in association with about 300 000 plant species in 90% of families (Smith and Read 1997), indicating that AM fungi are capable of colonizing many host species. Approximately 150 of the described mycorrhizal species may occur in sand dunes (Koske et al. 2004). Most host–fungus associations are beneficial to both the plant and the fungus and are thus regarded as mutualistic (++); however, the widespread use of the term mutualism (mutual benefit) for mycorrhizal interactions has been questioned because all associations are not beneficial to both the plant and fungus (Brundrett 2004).

Overexpression of MdIAA24 improves apple drought resistance by positively regulating strigolactone biosynthesis and mycorrhization

2020 ◽  
Author(s):  
Dong Huang ◽  
Qian Wang ◽  
Guangquan Jing ◽  
Mengnan Ma ◽  
Chao Li ◽  
...  
Keyword(s):  
Drought Stress ◽  
Positive Impact ◽  
Growth Parameters ◽  
Arbuscular Mycorrhizal ◽  
Am Fungi ◽  
Land Plant ◽  
Exchange Capacity ◽  
Cortical Cells ◽  
Relative Water ◽  
Am Symbiosis

Abstract Most land plant species have the ability to establish a symbiosis with arbuscular mycorrhizal (AM) fungi. These fungi penetrate into root cortical cells and form branched structures (known as arbuscules) for nutrient exchange. We cloned the MdIAA24 from apple (Malus domestica) following its up-regulation during AM symbiosis. Results demonstrate the positive impact of the overexpression (OE) of MdIAA24 in apple on AM colonization. We observed the strigolactone (SL) synthesis genes, including MdD27, MdCCD7, MdCCD8a, MdCCD8b and MdMAXa, to be up-regulated in the OE lines. Thus, the OE lines exhibited both a higher SL content and colonization rate. Furthermore, we observed that the OE lines were able to maintain better growth parameters under AM inoculation conditions. Under drought stress with the AM inoculation, the OE lines were less damaged, which was demonstrated by a higher relative water content, a lower relative electrolytic leakage, a greater osmotic adjustment, a higher reactive oxygen species scavenging ability, an improved gas exchange capacity and an increased chlorophyll fluorescence performance. Our findings demonstrate that the OE of MdIAA24 in apple positively regulates the synthesis of SL and the formation of arbuscules as a drought stress coping mechanism.

ELEMENT DISTRIBUTION IN HEAVY METAL STRESSED CRYO-SECTIONS OF GEOSIPHON PYRIFORME

2002 ◽  
Vol 12 (03n04) ◽  
pp. 151-158
Author(s):  
STEFAN SCHELOSKE ◽  
THORSTEN SCHNEIDER ◽  
ARTHUR SCHÜßLER
Keyword(s):  
Heavy Metal ◽  
Metal Uptake ◽  
Arbuscular Mycorrhizal ◽  
Am Fungi ◽  
Land Plant ◽  
Element Distribution ◽  
Point Of View ◽  
Heavy Metal Uptake ◽  
Blue Green Algae ◽  
Geosiphon Pyriforme

Geosiphon pyriforme is a unique symbiosis between a fungus, belonging to the arbuscular mycorrhizal (AM) fungi, and a cyanobacteria (blue-green algae). Since more than 80 % of the land plant species form an AM, the importance of this symbiosis becomes evident. In our research on heavy metal uptake and resistance of plants, Geosiphon is used as a model system for the AM symbiosis. Whilst we have studied heavy metal uptake of Geosiphon pyriforme from a macroscopic point of view we will now present first and preliminary results of element distributions in heavy metal stressed and non-stressed cryo-sections of Geoslphon pyriforme.

scholarly journals Phytohormone production by the arbuscular mycorrhizal fungus Rhizophagus irregularis

2020 ◽  
Author(s):  
Simon Pons ◽  
Sylvie Fournier ◽  
Christian Chervin ◽  
Guillaume Bécard ◽  
Soizic Rochange ◽  
...  
Keyword(s):  
Arbuscular Mycorrhizal Fungus ◽  
Mycorrhizal Fungus ◽  
Arbuscular Mycorrhizal ◽  
Am Fungi ◽  
Rhizophagus Irregularis ◽  
Mycorrhizal Symbiosis ◽  
Potential Contribution ◽  
Mutualistic Interaction ◽  
Isopentenyl Adenosine ◽  
Acid Pathway

AbstractArbuscular mycorrhizal symbiosis is a mutualistic interaction between most land plants and fungi of the glomeromycotina subphylum. The initiation, development and regulation of this symbiosis involve numerous signalling events between and within the symbiotic partners. Among other signals, phytohormones are known to play important roles at various stages of the interaction. During presymbiotic steps, plant roots exude strigolactones which stimulate the fungus, and favour the initiation of symbiosis. At later stages, different plant hormone classes can act as positive or negative regulators of the interaction. Although the fungus is known to reciprocally emit regulatory signals, its potential contribution to the phytohormonal pool has received little attention, and has so far only been addressed by indirect assays. In this study, using mass spectrometry, we analyzed phytohormones released into the medium by germinated spores of the arbuscular mycorrhizal fungus Rhizophagus irregularis. We detected the presence of a cytokinin (isopentenyl-adenosine) and an auxin (indole-acetic acid). In addition, we identified a gibberellin (gibberellic acid 4) in spore extracts. We also used gas chromatography to show that R. irregularis produces ethylene from methionine and the α-keto γ-methylthiobutyric acid pathway. These results highlight the possibility for AM fungi to use phytohormones to interact with their host plants, or to regulate their own development.

scholarly journals Histone H1 prevents non-CG methylation-mediated small RNA biogenesis in Arabidopsis heterochromatin

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Jaemyung Choi ◽  
David B Lyons ◽  
Daniel Zilberman
Keyword(s):  
Dna Methylation ◽  
Transposable Elements ◽  
Small Rna ◽  
Histone H3 ◽  
Histone H1 ◽  
Dna Methyltransferases ◽  
Flowering Plants ◽  
Genomic Sequences ◽  
Rna Molecules ◽  
Rna Biogenesis

Flowering plants utilize small RNA molecules to guide DNA methyltransferases to genomic sequences. This RNA-directed DNA methylation (RdDM) pathway preferentially targets euchromatic transposable elements. However, RdDM is thought to be recruited by methylation of histone H3 at lysine 9 (H3K9me), a hallmark of heterochromatin. How RdDM is targeted to euchromatin despite an affinity for H3K9me is unclear. Here we show that loss of histone H1 enhances heterochromatic RdDM, preferentially at nucleosome linker DNA. Surprisingly, this does not require SHH1, the RdDM component that binds H3K9me. Furthermore, H3K9me is dispensable for RdDM, as is CG DNA methylation. Instead, we find that non-CG methylation is specifically associated with small RNA biogenesis, and without H1 small RNA production quantitatively expands to non-CG methylated loci. Our results demonstrate that H1 enforces the separation of euchromatic and heterochromatic DNA methylation pathways by excluding the small RNA-generating branch of RdDM from non-CG methylated heterochromatin.

scholarly journals Effects of Arbuscular Mycorrhizal Fungi on Gazania rigens Pot Plant Cultivation in a Mediterranean Environment

2018 ◽  
Vol 47 (1) ◽  
pp. 221-226 ◽  
Author(s):  
Leo SABATINO ◽  
Fabio D’ANNA ◽  
Livio TORTA ◽  
Giorgio FERRARA ◽  
Giovanni IAPICHINO
Keyword(s):  
Mycorrhizal Fungi ◽  
Arbuscular Mycorrhizal ◽  
Am Fungi ◽  
Dry Weight ◽  
Rhizophagus Irregularis ◽  
High Performing ◽  
Beneficial Effects ◽  
Bedding Plants ◽  
Plant Cultivation ◽  
Bedding Plant

Herbaceous plants used in island beds and borders need to be rapid growing, high performing and maintaining good visual quality during the growing season. Arbuscular mycorrhizal (AM) fungi application is acquiring interest for its beneficial effects on ornamental bedding plants. Gazania rigens is a herbaceous ornamental plant grown for its large daisy-like flowers. The species thrives in the coastal areas of the Mediterranean region, particularly in the mild climate of southern Italy and Sicily, where performs well in summer bedding schemes in sea side gardens even in dry and windy conditions. The aim of this study was to evaluate the effect of inoculation with Rhizophagus irregularis on several ornamental parameters of Gazania rigens. Prior to transplanting, three-months-old plants received a mycorrhizal inoculum carrying 40 spores g-1 of Rhizophagus irregularis. Inoculum was applied at a rate of 10 g plant-1. The AM application significantly increased number of flowers per clump by 100% and number of flowers per plant by 124.0%. Rhizophagus irregularis also positively influenced number of leaves per plant, plant height, and roots dry weight. Our findings indicated that mycorrhizal inoculation with R. irregularis may be beneficial to nursery growers wishing to produce high quality gazania for spring-summer bedding plant schemes.

scholarly journals Constraining the role of early land plants in Palaeozoic weathering and global cooling

2015 ◽  
Vol 282 (1813) ◽  
pp. 20151115 ◽  
Author(s):  
Joe Quirk ◽  
Jonathan R. Leake ◽  
David A. Johnson ◽  
Lyla L. Taylor ◽  
Loredana Saccone ◽  
...  
Keyword(s):  
Arbuscular Mycorrhizal ◽  
Am Fungi ◽  
Land Plant ◽  
Network Size ◽  
Mineral Weathering ◽  
Land Plants ◽  
Tree Roots ◽  
Plant Fossils ◽  
Terrestrial Environments ◽  
Early Land

How the colonization of terrestrial environments by early land plants over 400 Ma influenced rock weathering, the biogeochemical cycling of carbon and phosphorus, and climate in the Palaeozoic is uncertain. Here we show experimentally that mineral weathering by liverworts—an extant lineage of early land plants—partnering arbuscular mycorrhizal (AM) fungi, like those in 410 Ma-old early land plant fossils, amplified calcium weathering from basalt grains threefold to sevenfold, relative to plant-free controls. Phosphate weathering by mycorrhizal liverworts was amplified 9–13-fold over plant-free controls, compared with fivefold to sevenfold amplification by liverworts lacking fungal symbionts. Etching and trenching of phyllosilicate minerals increased with AM fungal network size and atmospheric CO 2 concentration. Integration of grain-scale weathering rates over the depths of liverwort rhizoids and mycelia (0.1 m), or tree roots and mycelia (0.75 m), indicate early land plants with shallow anchorage systems were probably at least 10-fold less effective at enhancing the total weathering flux than later-evolving trees. This work challenges the suggestion that early land plants significantly enhanced total weathering and land-to-ocean fluxes of calcium and phosphorus, which have been proposed as a trigger for transient dramatic atmospheric CO 2 sequestration and glaciations in the Ordovician.

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